Is Human Culture Shaping Evolution?

A New York Times article reveals that human populations have been shaped not only by genes, but also by culture, which scientists say is a powerful force of natural selection.

The idea that genes and culture co-evolve has been around for several decades but has started to win converts only recently.

Two leading proponents, Robert Boyd of the University of California in Los Angeles and Peter J. Richerson of the University of California in Davis have argued for years that genes and culture were intertwined in shaping human evolution, reports The New York Times.

The best evidence available to Dr. Boyd and Dr. Richerson for culture being a selective force was the lactose tolerance found in many northern Europeans.

Most people switch off the gene that digests the lactose in milk shortly after they are weaned, but in northern Europeans — the descendants of an ancient cattle-rearing culture that emerged in the region some 6,000 years ago — the gene is kept switched on in adulthood.

Lactose tolerance is now well recognized as a case in which a cultural practice — drinking raw milk — has caused an evolutionary change in the human genome.

Presumably the extra nutrition was of such great advantage that adults able to digest milk left more surviving offspring, and the genetic change swept through the population.

This instance of gene-culture interaction turns out to be far from unique.

Many of the genes under selection seem to be responding to conventional pressures. Some are involved in the immune system, and presumably became more common because of the protection they provided against disease. Genes that cause paler skin in Europeans or Asians are probably a response to geography and climate.

But other genes seem to have been favored because of cultural changes. These include many genes involved in diet and metabolism and presumably reflect the major shift in diet that occurred in the transition from foraging to agriculture that started about 10,000 years ago.

Culture has become a force of natural selection, and if it should prove to be a major one, then human evolution may be accelerating as people adapt to pressures of their own creation.